I have 1K miles on this change after 4mo. When the car is used it always gets at least 100mi of highway driving, 99Acura CL. Car is garaged and temp is 60-88.
I usually change at 4mo or 4K.

Can I use this oil for another 4mo??

Dear Smoky,

Change extension is possible, but you need Lab oil analysis to see if this is safe.

A few that we know:
http://www.pdma.com/oil.html
http://www.testoil.com/
http://www.predictusa.com/
http://www.wearcheck.com/services/
http://www.analystsinc.com
http://wetestit.com/
http://www.herguth.com/
http://www.intertek-cb.com/ Maybe more than you need
http://www.staveleyna.com/

Test first/ ask for help from the lab/ make a good decision.